Gas turbine engines conventionally include pressurised oil systems for delivering oil to the components of the engine which require lubrication, such as the bearings and gearbox, for example. In use, the oil is pumped from an engine oil tank to the components and, during lubrication, air is entrained in the oil flow thus forming an air/oil mixture.
Since the oil system is a closed loop system, the air/oil mixture is returned to the oil tank. Since it is undesirable for the oil in the tank to contain air, an air/oil separator, also known as a de-aerator, is used to separate the air/oil mixture.
It is known to locate a centrifugal air/oil separator within an oil tank to separate the air/oil mixture returning to the tank. A known air/oil separator comprises a cylindrical separation chamber in which separation of the air/oil mixture occurs. An air outlet for discharging separated air is located within the separation chamber, and separated oil returns to the tank from an open end of the chamber.
One disadvantage of this known air/oil separator is that oil is entrained in the flow of separated air and is discharged from the air outlet with the air. Another disadvantage is that the separated oil discharged from the separator causes disturbance of the oil already present in the oil tank.
It would therefore be desirable to provide a centrifugal gas/liquid separator which minimises the amount of liquid discharged with the separated gas and also minimises the disturbance of the liquid in the reservoir in which the separator is located.